Field
The present technology relates to fabrication of semiconductor devices.
Description of Related Art
Wire bonding is a primary method of electrically coupling two separate electronic components such as semiconductor die or a substrate during semiconductor device fabrication.
During a wire bonding process, a length of wire (typically gold or copper) is fed through a central cavity of a needle-like disposable tool called the capillary. The wire protrudes through a tip of the capillary, where a high-voltage electric charge is applied to the wire from a transducer associated with the capillary tip. The electric charge melts the wire at the tip and the wire forms into a ball owing to the surface tension of the molten metal. As the ball solidifies, the capillary is lowered to bonding surface and ultrasonic energy is applied by the transducer. The bonding surface can also be heated to facilitate bonding. The combined heat, pressure, and ultrasonic energy create a weld between the copper or gold ball and the bonding surface. The capillary is then pulled up and away from the bonding surface, as the wire is passed out through the capillary. The resulting bond is referred as a ball bond. The bonding surface may be a die bonding pad of a semiconductor die, a contact pad of a substrate, or even another previous formed ball bond structure.
The capillary carrying the wire then moves over to another bonding surface such as next die bonding pad of adjacent semiconductor die or a contact pad of substrate, and descends and crushes the wire by touching the bonding surface to make the wire bond again using heat, pressure and ultrasonic energy. The capillary then pays out a small length of wire and tears the wire from the bonding surface. The resulting bond is often referred as a wedge bond, or a stitch bond.